In certain types of treatments such as fracturing, a series of barriers with ball seats are used for the purpose of sequentially isolating intervals that have already been fractured so that the next interval uphole can be perforated and fractured. Typical of such plug devices is Us2013/0000914. Here sleeves are expanded that have an external seal and a lower end ball seat. At the end of the fracturing operation all the sleeves that were used have to be milled out.
US 2014/0014339 shows the use of a plug with an external rubber seal that is expanded with a swage moved by a wireline setting tool where the swage has a ball seat and is made of a disintegrating material. The design uses a shear device to the setting tool mandrel that remains behind as well as a rubber sleeve.
U.S. Pat. No. 7,784,797 shows the use of hardened insert segments with square bases that are dropped into an associated recess and then overlaid with rubber to retain the insert for running in. On setting, the hardened particles emerge through the rubber to aid in fixation of the expanded liner hanger. This being a liner hanger installation there is no need for any components to later disintegrate.
Several features are included in the present invention such as the use of degradable ribs without any seals for a fracturing application. While the ribs alone may not create a perfect seal on expansion and may not penetrate the surrounding tubular, a fracturing application can tolerate some leakage as long as the required flow can be delivered at the needed pressure to the formation. Additionally hardened materials, while having a benefit to enhance wall penetration into the surrounding tubular for enhanced grip are still limited in their degree of expansion and are not materials that are degradable. This can then leave residue when degrading other parts of a fracturing plug. The design of the shear tab from the fracturing plug is such that it extends into a mandrel of the setting tool that is removed from the plug when using a wireline setting tool such as the E-4 setting tool offered by Baker Hughes Incorporated of Houston, Tex.
An alternative design features the use of flexing ribs that do not necessarily penetrate the wall of the surrounding tubular but that can be made of a disintegrating material. These are combined with an o-ring seal to minimize the non-degrading parts when the plug is no longer needed and has to be removed to facilitate other completion steps or production. Hardened inserts are provided at a spaced location from the o-ring. The inserts can be in the shape of a c-ring and spread and snapped in or using flexing of an adjacent rib inserted as discrete units to be retained with a potential energy force from the adjacent flexed rib. The discrete units are multiple segments cut from a continuous ring. Cutting the ring into several segments reduces the space between hardened inserts after the sleeve is swaged over a cone. Reducing the distance that there is not external support for the cone will reduce the likelihood that the cone will fail when hydraulic pressure is applied to the plug. While the hardened inserts and the o-rings do not disintegrate the bulk of the plug will disintegrate facilitating subsequent operations. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.